1. Field of the Invention
The present invention relates to a direct injection diesel engine mainly as regards the construction of the combustion chamber and its distribution and injection fittings.
2. Discussion of the Prior Art
In a first class of diesel engine of known type, each piston is covered by a cylinder head in which four valves are fitted (two valves for the inlet, two valves for the exhaust). In the central area situated between the four valves there is a mechanically controlled injector of which the axis is aligned perpendicularly to the plane of the cylinder head gasket. The mechanically controlled injector pump is supplied with fuel at low pressure, and is controlled by a camshaft located in the cylinder head or in the engine block which pressurizes the fuel so that the fuel is injected at very high pressure into the combustion chamber.
The advantages of the mechanically controlled injector are known, as it allows, among other things, the use of extremely short channels for the high pressure fuel circuit. Among other results, this generally avoids the use of any variator to adjust the injection advance automatically in relation to the speed of rotation of the engine.
The quality of the atomization and mixing of the fuel with the air in the cylinder is mainly insured by the nozzle of the mechanically controlled injector. This leads to the use of a relatively expensive and complicated nozzle, comprising principally including several drillings of extremely small diameter, which is difficult to manufacture. In addition, it is established that this type of injector cannot be used on engines of small bore.
In a second class of diesel engine of known type, the cylinder head has two valves per cylinder (an inlet valve and an exhaust valve). The inlet of air is introduced tangentially into the combustion chamber so as to create a large turbulence. The injector then is in an eccentric position and is an injector fed in the conventional manner by a high pressure channel of relatively great length. All the channels corresponding to the different cylinders of the engine are connected to a central injection pump. The advantages and disadvantages of this conventional injection system are known, it generally leading to the fitting to the pump of an automatic advance variator operating in relation to the speed of the engine. Such a diesel engine cylinder head is described in my earlier U.S. Pat. No. 4,214,560 issued July 29, 1980, now owned by the assignee of the present application under the title "Cylinder Head Improvement, Particularly For a Diesel Engine".